The present invention relates to a search type tuning device of the type using a voltage-controlled oscillator for automatically tuning its oscillation frequency to a predetermined frequency.
In the conventional so-called search type tuning devices, the input signal is amplified by a high frequency amplifier, and is converted by a mixer with the output from a local oscillator into an intermediate frequency signal. The intermediate frequency signal passes through a frequency discriminator, a low-pass filter and a voltage sweep control circuit and is applied to a voltage sweeper or voltage sweeping circuit to control it. When the local oscillator sweeps its oscillation frequency to a predetermined frequency, the voltage sweep is stopped so that the desired input signal is selected and received. However, in the conventional search type tuning devices of such type as described, a voltage sweep control circuit has non-linear characteristics so that the analysis of the tuning device for determining the characteristics thereof is difficult. Furthermore, they have an undesirable characteristic in that a high speed search tuning cannot be attained.